SSM(三)Mybatis动态SQL

1.查询语句，where：

<resultMap id="xxx" type="xx..Student" autoMapping="false">...</resultMap>
<select id="findAll" resultMap="xxx">
    select * from student
    <where>
        <if test="stuNo!=null and stuNo!=''">and stuNo=#{stuNo}</if>
        <if test="stuName!=null and stuName!=''">and stuName like '%' #{stuName} '%'</if>
    </where>
</select>

2.插入语句，trim：

<insert id="saveAttendances">
        insert into tms_attendance
                <trim prefix="(" suffixOverrides="," suffix=")">
                    <if test="at_tid != null">at_tid,</if>
                    <if test="at_labnum != null">at_labnum,</if>
                    ...
                </trim>
            VALUES
        <trim prefix="(" suffixOverrides="," suffix=")">
            <if test="at_tid != null">#{at_tid},</if>
            <if test="at_labnum != null">#{at_labnum},</if>
            ...
        </trim>
    </insert>

3.修改语句，trim：

<update id="editUserById" parameterType="cn.happy.entity.Smbms_user">
        update smbms_user
                <trim prefix="set" suffixOverrides=",">
                    <if test="username !=null and username !=''">userName=#{username},</if>
                    <if test="userpassword !=null">userPassword=#{userpassword},</if>
                </trim>
        where id=#{id}
    </update>

 4.查询语句，foreach：

<select id="findByList" resultType="Student">
    select * from student
    <if test="list.size>0">
        WHERE stuno in
        <foreach collection="list" open="(" close=")" separator="," item="myid">
            #{myid}
        </foreach>
    </if>
</select>